The European Central Bank proudly announced on Friday that it is erecting a 17-metre-high bronze and granite tree outside its Frankfurt headquarters – an artwork intended to “convey a sense of stability and growth” – and, with its gilded leaves and massive trunk, presumably also wealth and power.

But when Mario Draghi, the ECB’s president, appeared before the world’s media on Thursday at his regular press conference, it was the limit to central bankers’ power that was on display.

Draghi was forced to admit that the outlook for eurozone growth and inflation had darkened considerably as a result of the slowdown in emerging economies and the market turmoil in China – the latter an issue he said he would take up with officials at the People’s Bank of China at this weekend’s G20 meeting in Ankara.

Meanwhile, Federal Reserve policymakers will have to decide in the coming days whether to stick to their carefully signalled plan to push up America’s interest rates at their next policy meeting on 17 September, in the face of growing fears about a Chinese slowdown.

Certainly, the International Monetary Fund made it clear last week that it believed policymakers should be cautious about pushing up rates in the current fragile environment.

Central bankers slashed rates to their current emergency levels in the depths of the crisis. They also unleashed quantitative easing on a massive scale, as a short-term measure meant to prevent an outright economic slump and buy time for other engines of growth – trade, investment, consumer demand – to be restarted.

Yet even with rock-bottom borrowing costs, the recovery in many countries has been tepid, leaving central bankers little choice but to keep the cash taps on. The ECB and the Japanese central bank are still quantitatively easing; and the Bank of England and the Fed are yet to raise rates, seven years on from the collapse of Lehman Brothers. Whatever the diagnosis for the less-than-impressive post-crisis recovery – the debt overhang from the boom years, chronic underinvestment, weak consumer demand as a result of deep-seated inequality, or some other as yet undiagnosed economic disease – the cure is unlikely to lie with the central banks.

Yet they remain the first line of defence against any new crisis despite having little ammunition left. And while they like to cherish the illusion they are as solid and stable as that massive bronze and granite tree, central bankers on both sides of the Atlantic are being battered by the chill winds of the Chinese slowdown.

In his speech to the annual central bankers’ talkfest last weekend in Jackson Hole, Wyoming, Mark Carney, the Bank of England’s governor, stressed the powers central banks still have it in their hands to shape their nations’ economic destiny, despite global economic interdependence and the turbulent market backdrop. He insisted: “Developments in China are unlikely to change the process of rate increases from limited and gradual to infinitesimal and inert.”

Yet the dominoes that have been falling in emerging economies in recent weeks – with share prices and currencies pummelled, demand for exports hit and growth forecasts slashed – have been as clear a signal as anyone could hope for that the world is far from ready to withstand tighter monetary policy.

And the market gyrations of recent weeks have been a reminder of a lesson the world learned in the crisis of 2008 and beyond: central banks are not the omniscient puppet masters of the global economy they seemed before the crash. Instead, in resorting to trillions of dollars’ worth of quantitative easing, they may have conjured up forces they can barely control.

The Fed may yet press ahead with its rate rise later this month; but as the markets continue to fret about the prospects of a Chinese slump, expect to see plenty more evidence that central bankers, unlike that rock-solid Frankfurt tree, are sometimes forced to bend with the wind.

… and even Waitrose is starting to feel the chill

Waitrose is expected to report its first fall in like-for-like sales for seven years this week when the John Lewis Partnership reveals half-year results. The slide will highlight that the pain for supermarkets is far from over.

Waitrose has been one of the top performers, alongside discounters Aldi and Lidl, since the financial crisis in 2007. But with prices falling – partly due to lower commodity prices and partly due to the “big four” taking on the discounters – the value of grocery sales is being dragged down.

For Tesco and Morrisons, whose sales and profits have tumbled in the last year, Waitrose’s figures show there is no light at the end of the tunnel.

David Potts, Morrisons’s new boss, will lay out his turnaround plans this week. But in a market when even Waitrose is struggling, Potts has a long, hard road ahead.

But Laura Wade-Gery, head of online operations at Marks & Spencer, and Marissa Mayer, boss of Yahoo have both made headlines by preparing to take maternity leave.

True, the two women are a little unusual. Wade-Gery is becoming a first-time mum at 50, while Mayer, although she is expecting twins, is pledging to take only two weeks’ maternity leave.

Even so, the fact that two women taking time off can generate such interest reflects the sorry fact there are so few them at the top of the corporate ladder. It was only in 2001 that the stock market had to deal with this for the first time when Belinda Earl, at the time the boss of Debenhams, became the first chief executive of a listed company to take maternity leave. A year Kingfisher felt impelled to announce that Helen Weir – now also at M&S – had gone on maternity leave. When Katherine Garrett-Cox was appointed chief investment officer at Aberdeen Asset Management in 2000, eyebrows were raised in some areas of the City when she revealed she was pregnant with her second child and would be off for four months.

The fact that, 15 years on, maternity leave for senior women is still a story shows that much more needs to be done to push women up the corporate ladder and change public attitudes to women in high-profile roles.

Some women become mothers; some don’t. Some men have their first child at 50; some take two weeks off when they become a father of twins. Only when none of the above is news will there be real equality.